The present invention concerns a new and improved construction of watercraft with swivel fin drive, for which a propulsion fin is provided, which is swivellable laterally by a drive equipment and which, from its vertical swivel axle, extends parallel to the longitudinal direction of the watercraft.
Such watercrafts, the propulsion motions of which often take place through muscular power of the user, are in themselves known in the art. In these state-of-the-art watercraft, the propulsion fin consists of a separate element. Such is generally produced of flexible material and is fastened to a vertical swivel lever underneath the watercraft. A vertical prolongation of this swivel lever extends upwardly into the interior of the watercraft and is guided rotatably in the boat shell. This prolongation of the swivel lever is driven by drive equipment which is provided in the interior of the boat or on the deck. An example of application of such swivel fin drive for a watercraft is disclosed in German patent publication No. 2,440,369. In the case of this exemplary field of application, the drive fin is disposed directly behind the keel of the watercraft.
The arrangement of a laterally swivellable propulsion fin underneath the watercraft has the disadvantage of requiring a great deal of space. Furthermore, a certain risk results therefrom of damaging the mechanism consisting of propulsion fin, swivel lever and associated drive equipment. Thus, for example, during transport, the swivel lever can be bent, whereby the mechanism would no longer function properly. A relatively great draft also results from this arrangement of the propulsion fin, for which reason the watercraft cannot be used in shallow waters. The propulsion fin, which is moved relatively far laterally below the water level, requires that the floating body or hull of the watercraft is dimensioned to be large, in order to impart to the watercraft the necessary lateral stability. The swivel lever guided from below through the shell or hull of the boat presupposes a perfect and durable sealing of this penetration point. This sealing is difficult to execute and consequently makes the watercraft more expensive.